text: //=================================================================================================
  /*!
  //  \file blaze/math/lapack/clapack/gges.h
  //  \brief Header file for the CLAPACK gges wrapper functions
  //
  //  Copyright (C) 2012-2019 Klaus Iglberger - All Rights Reserved
  //
  //  This file is part of the Blaze library. You can redistribute it and/or modify it under
  //  the terms of the New (Revised) BSD License. Redistribution and use in source and binary
  //  forms, with or without modification, are permitted provided that the following conditions
  //  are met:
  //
  //  1. Redistributions of source code must retain the above copyright notice, this list of
  //     conditions and the following disclaimer.
  //  2. Redistributions in binary form must reproduce the above copyright notice, this list
  //     of conditions and the following disclaimer in the documentation and/or other materials
  //     provided with the distribution.
  //  3. Neither the names of the Blaze development group nor the names of its contributors
  //     may be used to endorse or promote products derived from this software without specific
  //     prior written permission.
  //
  //  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
  //  EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  //  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
  //  SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  //  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  //  TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  //  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  //  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  //  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  //  DAMAGE.
  */
  //=================================================================================================
  
  #ifndef _BLAZE_MATH_LAPACK_CLAPACK_GGES_H_
  #define _BLAZE_MATH_LAPACK_CLAPACK_GGES_H_
  
  
  //*************************************************************************************************
  // Includes
  //*************************************************************************************************
  
  #include <blaze/util/Complex.h>
  #include <blaze/util/StaticAssert.h>
  #include <blaze/util/Types.h>
  
  
  //=================================================================================================
  //
  //  LAPACK FORWARD DECLARATIONS
  //
  //=================================================================================================
  
  //*************************************************************************************************
  /*! \cond BLAZE_INTERNAL */
  #if !defined(INTEL_MKL_VERSION)
  extern "C" {
  
  void sgges_( char* jobvsl, char* jobvsr, char* sort,
               int (*selctg)( const float*, const float*, const float* ), int* n,
               float* A, int* lda, float* B, int* ldb, int* sdim, float* alphar, float* alphai,
               float* beta, float* VSL, int* ldvsl, float* VSR, int* ldvsr, float* work,
               int* lwork, int* bwork, int* info, blaze::fortran_charlen_t njobvsl,
               blaze::fortran_charlen_t njobvsr, blaze::fortran_charlen_t nsort );
  void dgges_( char* jobvsl, char* jobvsr, char* sort,
               int (*selctg)( const double*, const double*, const double* ), int* n,
               double* A, int* lda, double* B, int* ldb, int* sdim, double* alphar, double* alphai,
               double* beta, double* VSL, int* ldvsl, double* VSR, int* ldvsr, double* work,
               int* lwork, int* bwork, int* info, blaze::fortran_charlen_t njobvsl,
               blaze::fortran_charlen_t njobvsr, blaze::fortran_charlen_t nsort );
  void cgges_( char* jobvsl, char* jobvsr, char* sort,
               int (*selctg)( const float*, const float* ), int* n,
               float* A, int* lda, float* B, int* ldb, int* sdim, float* alpha, float* beta,
               float* VSL, int* ldvsl, float* VSR, int* ldvsr, float* work, int* lwork,
               float* rwork, int* bwork, int* info, blaze::fortran_charlen_t njobvsl,
               blaze::fortran_charlen_t njobvsr, blaze::fortran_charlen_t nsort );
  void zgges_( char* jobvsl, char* jobvsr, char* sort,
               int (*selctg)( const double*, const double* ), int* n,
               double* A, int* lda, double* B, int* ldb, int* sdim, double* alpha, double* beta,
               double* VSL, int* ldvsl, double* VSR, int* ldvsr, double* work, int* lwork,
               double* rwork, int* bwork, int* info, blaze::fortran_charlen_t njobvsl,
               blaze::fortran_charlen_t njobvsr, blaze::fortran_charlen_t nsort );
  
  }
  #endif
  /*! \endcond */
  //*************************************************************************************************
  
  
  
  
  namespace blaze {
  
  //=================================================================================================
  //
  //  LAPACK GENERALIZED SCHUR DECOMPOSITION FUNCTIONS (GGES)
  //
  //=================================================================================================
  
  //*************************************************************************************************
  /*!\name LAPACK generalized Schur decomposition functions (gges) */
  //@{
  void gges( char jobvsl, char jobvsr, char sort,
             int (*selctg)( const float*, const float*, const float* ), int n, float* A, int lda,
             float* B, int ldb, int* sdim, float* alphar, float* alphai, float* beta, float* VSL,
             int ldvsl, float* VSR, int ldvsr, float* work, int lwork, int* bwork, int* info );
  
  void gges( char jobvsl, char jobvsr, char sort,
             int (*selctg)( const double*, const double*, const double* ), int n, double* A, int lda,
             double* B, int ldb, int* sdim, double* alphar, double* alphai, double* beta, double* VSL,
             int ldvsl, double* VSR, int ldvsr, double* work, int lwork, int* bwork, int* info );
  
  void gges( char jobvsl, char jobvsr, char sort,
             int (*selctg)( const complex<float>*, const complex<float>* ), int n,
             complex<float>* A, int lda, complex<float>* B, int ldb, int* sdim,
             complex<float>* alpha, complex<float>* beta, complex<float>* VSL, int ldvsl,
             complex<float>* VSR, int ldvsr, complex<float>* work, int lwork, float* rwork,
             int* bwork, int* info );
  
  void gges( char jobvsl, char jobvsr, char sort,
             int (*selctg)( const complex<double>*, const complex<double>* ), int n,
             complex<double>* A, int lda, complex<double>* B, int ldb, int* sdim,
             complex<double>* alpha, complex<double>* beta, complex<double>* VSL, int ldvsl,
             complex<double>* VSR, int ldvsr, complex<double>* work, int lwork, double* rwork,
             int* bwork, int* info );
  //@}
  //*************************************************************************************************
  
  
  //*************************************************************************************************
  /*!\brief LAPACK kernel for computing the generalized Schur decomposition for a pair of
  //        non-symmetric single precision column-major matrices.
  // \ingroup lapack_eigenvalue
  //
  // \param jobvsl \c 'V' to compute the left Schur vectors, \c 'N' to not compute them.
  // \param jobvsr \c 'V' to compute the right Schur vectors, \c 'N' to not compute them.
  // \param sort \c 'S' to order the eigenvalues on the diagonal, \c 'N' to not order them (see \a selctg).
  // \param selctg Logical function of three single precision arguments.
  // \param n The order of the matrices \a A, \a B, \a VSL, and \a VSR \f$[0..\infty)\f$.
  // \param A Pointer to the first element of the single precision column-major matrix \a A.
  // \param lda The total number of elements between two columns of the matrix A; size >= max( 1, \a n ).
  // \param B Pointer to the first element of the single precision column-major matrix \a B.
  // \param ldb The total number of elements between two columns of the matrix B; size >= max( 1, \a n ).
  // \param sdim Returns the number of eigenvalues (after sorting) for which \a selctg is \a true.
  // \param alphar Pointer to the first element of the real part of the eigenvalue numerator; size == n.
  // \param alphai Pointer to the first element of the imaginary part of the eigenvalue numerator; size == n.
  // \param beta Pointer to the first element of the eigenvalue denominator; size == n.
  // \param VSL Pointer to the first element of the column-major matrix for the left Schur vectors.
  // \param ldvsl The total number of elements between two columns of the matrix VSL \f$[0..\infty)\f$.
  // \param VSR Pointer to the first element of the column-major matrix for the right Schur vectors.
  // \param ldvsr The total number of elements between two columns of the matrix VSR \f$[0..\infty)\f$.
  // \param work Auxiliary array; size >= max( 1, \a lwork ).
  // \param lwork The dimension of the array \a work; see online reference for details.
  // \param bwork Auxiliary array; size == n.
  // \param info Return code of the function call.
  //
  // This function computes for a pair of \a n-by-\a n single precision non-symmetric matrices
  // (\a A,\a B) the generalized eigenvalues, the generalized real Schur form (\a S, \a T), and
  // optionally the left and/or right matrices of Schur vectors (\a VSL and \a VSR). This gives
  // the generalized Schur factorization
  
                        \f[ (A,B) = ( (VSL)*S*(VSR)**T, (VSL)*T*(VSR)**T ). \f]
  
  // Optionally, it also orders the eigenvalues such that a selected cluster of eigenvalues appears
  // in the leading diagonal blocks of the upper quasi-triangular matrix \a S and the upper triangular
  // matrix \a T. The leading columns of \a VSL and \a VSR then form an orthonormal basis for the
  // corresponding left and right eigenspaces (deflating subspaces).
  //
  // The parameter \a jobvsl specifies the computation of the left Schur vectors:
  //
  //   - \c 'V': The left Schur vectors of \a (A,B) are computed and returned in \a VSL.
  //   - \c 'N': The left Schur vectors of \a (A,B) are not computed.
  //
  // The parameter \a jobvsr specifies the computation of the right Schur vectors:
  //
  //   - \c 'V': The right Schur vectors of \a (A,B) are computed and returned in \a VSR.
  //   - \c 'N': The right Schur vectors of \a (A,B) are not computed.
  //
  // Via the parameter \a selctg it is possible to select specific eigenvalues. \a selctg is a
  // pointer to a function of three single precision floating point arguments returning an \c int
  // value. In case \a sort is set to \c 'N', \a selctg is not referenced, else if sort is set to
  // \c 'S' \a selctg is used to select eigenvalues to sort to the top left of the Schur form. An
  // eigenvalue \f$ (alphar[j]+alphai[j]*i)/beta[j] \f$ is selected if
  
     \code
     selctg( &alphar[j], &alphai[j], &beta[j])
     \endcode
  
  // evaluates to true; i.e. if either one of a complex conjugate pair of eigenvalues is selected,
  // then both complex eigenvalues are selected. On exit, the parameter \a sdim will contain the
  // number of eigenvalues (after sorting) for which \a selctg is \a true. Note that complex
  // conjugate pairs for which \a selctg is \a true for either eigenvalue count as 2.
  //
  // The \a info argument provides feedback on the success of the function call:
  //
  //   - = 0: The computation finished successfully.
  //   - < 0: If info = -i, the i-th argument had an illegal value.
  //   - > 1,...,\a n: The QZ iteration failed. (A,B) are not in Schur form, but \a alphar(j),
  //          \a alphai(j), and \a beta(j) should be correct for j=\a info,...,\a n-1.
  //   - > \a n: see online reference for details.
  //
  // For more information on the sgges() function, see the LAPACK online documentation browser:
  //
  //        http://www.netlib.org/lapack/explore-html/
  //
  // \note This function can only be used if a fitting LAPACK library, which supports this function,
  // is available and linked to the executable. Otherwise a call to this function will result in a
  // linker error.
  */
  inline void gges( char jobvsl, char jobvsr, char sort,
                    int (*selctg)( const float*, const float*, const float* ), int n,
                    float* A, int lda, float* B, int ldb, int* sdim, float* alphar, float* alphai,
                    float* beta, float* VSL, int ldvsl, float* VSR, int ldvsr, float* work,
                    int lwork, int* bwork, int* info )
  {
  #if defined(INTEL_MKL_VERSION)
     BLAZE_STATIC_ASSERT( sizeof( MKL_INT ) == sizeof( int ) );
  #endif
  
     sgges_( &jobvsl, &jobvsr, &sort, selctg, &n, A, &lda, B, &ldb, sdim, alphar, alphai, beta,
             VSL, &ldvsl, VSR, &ldvsr, work, &lwork, bwork, info
  #if !defined(INTEL_MKL_VERSION)
           , blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1)
  #endif
           );
  }
  //*************************************************************************************************
  
  
  //*************************************************************************************************
  /*!\brief LAPACK kernel for computing the generalized Schur decomposition for a pair of
  //        non-symmetric double precision column-major matrices.
  // \ingroup lapack_eigenvalue
  //
  // \param jobvsl \c 'V' to compute the left Schur vectors, \c 'N' to not compute them.
  // \param jobvsr \c 'V' to compute the right Schur vectors, \c 'N' to not compute them.
  // \param sort \c 'S' to order the eigenvalues on the diagonal, \c 'N' to not order them (see \a selctg).
  // \param selctg Logical function of three double precision arguments.
  // \param n The order of the matrices \a A, \a B, \a VSL, and \a VSR \f$[0..\infty)\f$.
  // \param A Pointer to the first element of the double precision column-major matrix \a A.
  // \param lda The total number of elements between two columns of the matrix A; size >= max( 1, \a n ).
  // \param B Pointer to the first element of the double precision column-major matrix \a B.
  // \param ldb The total number of elements between two columns of the matrix B; size >= max( 1, \a n ).
  // \param sdim Returns the number of eigenvalues (after sorting) for which \a selctg is \a true.
  // \param alphar Pointer to the first element of the real part of the eigenvalue numerator; size == n.
  // \param alphai Pointer to the first element of the imaginary part of the eigenvalue numerator; size == n.
  // \param beta Pointer to the first element of the eigenvalue denominator; size == n.
  // \param VSL Pointer to the first element of the column-major matrix for the left Schur vectors.
  // \param ldvsl The total number of elements between two columns of the matrix VSL \f$[0..\infty)\f$.
  // \param VSR Pointer to the first element of the column-major matrix for the right Schur vectors.
  // \param ldvsr The total number of elements between two columns of the matrix VSR \f$[0..\infty)\f$.
  // \param work Auxiliary array; size >= max( 1, \a lwork ).
  // \param lwork The dimension of the array \a work; see online reference for details.
  // \param bwork Auxiliary array; size == n.
  // \param info Return code of the function call.
  //
  // This function computes for a pair of \a n-by-\a n double precision non-symmetric matrices
  // (\a A,\a B) the generalized eigenvalues, the generalized real Schur form (\a S, \a T), and
  // optionally the left and/or right matrices of Schur vectors (\a VSL and \a VSR). This gives
  // the generalized Schur factorization
  
                        \f[ (A,B) = ( (VSL)*S*(VSR)**T, (VSL)*T*(VSR)**T ). \f]
  
  // Optionally, it also orders the eigenvalues such that a selected cluster of eigenvalues appears
  // in the leading diagonal blocks of the upper quasi-triangular matrix \a S and the upper triangular
  // matrix \a T. The leading columns of \a VSL and \a VSR then form an orthonormal basis for the
  // corresponding left and right eigenspaces (deflating subspaces).
  //
  // The parameter \a jobvsl specifies the computation of the left Schur vectors:
  //
  //   - \c 'V': The left Schur vectors of \a (A,B) are computed and returned in \a VSL.
  //   - \c 'N': The left Schur vectors of \a (A,B) are not computed.
  //
  // The parameter \a jobvsr specifies the computation of the right Schur vectors:
  //
  //   - \c 'V': The right Schur vectors of \a (A,B) are computed and returned in \a VSR.
  //   - \c 'N': The right Schur vectors of \a (A,B) are not computed.
  //
  // Via the parameter \a selctg it is possible to select specific eigenvalues. \a selctg is a
  // pointer to a function of three double precision floating point arguments returning an \c int
  // value. In case \a sort is set to \c 'N', \a selctg is not referenced, else if sort is set to
  // \c 'S' \a selctg is used to select eigenvalues to sort to the top left of the Schur form. An
  // eigenvalue \f$ (alphar[j]+alphai[j]*i)/beta[j] \f$ is selected if
  
     \code
     selctg( &alphar[j], &alphai[j], &beta[j])
     \endcode
  
  // evaluates to true; i.e. if either one of a complex conjugate pair of eigenvalues is selected,
  // then both complex eigenvalues are selected. On exit, the parameter \a sdim will contain the
  // number of eigenvalues (after sorting) for which \a selctg is \a true. Note that complex
  // conjugate pairs for which \a selctg is \a true for either eigenvalue count as 2.
  //
  // The \a info argument provides feedback on the success of the function call:
  //
  //   - = 0: The computation finished successfully.
  //   - < 0: If info = -i, the i-th argument had an illegal value.
  //   - > 1,...,\a n: The QZ iteration failed. (A,B) are not in Schur form, but \a alphar(j),
  //          \a alphai(j), and \a beta(j) should be correct for j=\a info,...,\a n-1.
  //   - > \a n: see online reference for details.
  //
  // For more information on the sgges() function, see the LAPACK online documentation browser:
  //
  //        http://www.netlib.org/lapack/explore-html/
  //
  // \note This function can only be used if a fitting LAPACK library, which supports this function,
  // is available and linked to the executable. Otherwise a call to this function will result in a
  // linker error.
  */
  inline void gges( char jobvsl, char jobvsr, char sort,
                    int (*selctg)( const double*, const double*, const double* ), int n,
                    double* A, int lda, double* B, int ldb, int* sdim, double* alphar, double* alphai,
                    double* beta, double* VSL, int ldvsl, double* VSR, int ldvsr, double* work,
                    int lwork, int* bwork, int* info )
  {
  #if defined(INTEL_MKL_VERSION)
     BLAZE_STATIC_ASSERT( sizeof( MKL_INT ) == sizeof( int ) );
  #endif
  
     dgges_( &jobvsl, &jobvsr, &sort, selctg, &n, A, &lda, B, &ldb, sdim, alphar, alphai, beta,
             VSL, &ldvsl, VSR, &ldvsr, work, &lwork, bwork, info
  #if !defined(INTEL_MKL_VERSION)
           , blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1)
  #endif
           );
  }
  //*************************************************************************************************
  
  
  //*************************************************************************************************
  /*!\brief LAPACK kernel for computing the generalized Schur decomposition for a pair of
  //        non-symmetric single precision complex column-major matrices.
  // \ingroup lapack_eigenvalue
  //
  // \param jobvsl \c 'V' to compute the left Schur vectors, \c 'N' to not compute them.
  // \param jobvsr \c 'V' to compute the right Schur vectors, \c 'N' to not compute them.
  // \param sort \c 'S' to order the eigenvalues on the diagonal, \c 'N' to not order them (see \a selctg).
  // \param selctg Logical function of two single precision complex arguments.
  // \param n The order of the matrices \a A, \a B, \a VSL, and \a VSR \f$[0..\infty)\f$.
  // \param A Pointer to the first element of the single precision complex column-major matrix \a A.
  // \param lda The total number of elements between two columns of the matrix A; size >= max( 1, \a n ).
  // \param B Pointer to the first element of the single precision complex column-major matrix \a B.
  // \param ldb The total number of elements between two columns of the matrix B; size >= max( 1, \a n ).
  // \param sdim Returns the number of eigenvalues (after sorting) for which \a selctg is \a true.
  // \param alpha Pointer to the first element of the eigenvalue numerator; size == n.
  // \param beta Pointer to the first element of the eigenvalue denominator; size == n.
  // \param VSL Pointer to the first element of the column-major matrix for the left Schur vectors.
  // \param ldvsl The total number of elements between two columns of the matrix VSL \f$[0..\infty)\f$.
  // \param VSR Pointer to the first element of the column-major matrix for the right Schur vectors.
  // \param ldvsr The total number of elements between two columns of the matrix VSR \f$[0..\infty)\f$.
  // \param work Auxiliary array; size >= max( 1, \a lwork ).
  // \param lwork The dimension of the array \a work; see online reference for details.
  // \param rwork Auxiliary array; size == 8*n.
  // \param bwork Auxiliary array; size == n.
  // \param info Return code of the function call.
  //
  // This function computes for a pair of \a n-by-\a n single precision complex non-symmetric
  // matrices (\a A,\a B) the generalized eigenvalues, the generalized real Schur form (\a S, \a T),
  // and optionally the left and/or right matrices of Schur vectors (\a VSL and \a VSR). This gives
  // the generalized Schur factorization
  
                        \f[ (A,B) = ( (VSL)*S*(VSR)**T, (VSL)*T*(VSR)**T ). \f]
  
  // Optionally, it also orders the eigenvalues such that a selected cluster of eigenvalues appears
  // in the leading diagonal blocks of the upper quasi-triangular matrix \a S and the upper triangular
  // matrix \a T. The leading columns of \a VSL and \a VSR then form an orthonormal basis for the
  // corresponding left and right eigenspaces (deflating subspaces).
  //
  // The parameter \a jobvsl specifies the computation of the left Schur vectors:
  //
  //   - \c 'V': The left Schur vectors of \a (A,B) are computed and returned in \a VSL.
  //   - \c 'N': The left Schur vectors of \a (A,B) are not computed.
  //
  // The parameter \a jobvsr specifies the computation of the right Schur vectors:
  //
  //   - \c 'V': The right Schur vectors of \a (A,B) are computed and returned in \a VSR.
  //   - \c 'N': The right Schur vectors of \a (A,B) are not computed.
  //
  // Via the parameter \a selctg it is possible to select specific eigenvalues. \a selctg is a
  // pointer to a function of two single precision complex arguments returning an \c int value.
  // In case \a sort is set to \c 'N', \a selctg is not referenced, else if sort is set to \c 'S'
  // \a selctg is used to select eigenvalues to sort to the top left of the Schur form. An
  // eigenvalue \f$ alpha[j]/beta[j] \f$ is selected if
  
     \code
     selctg( &alpha[j], &beta[j])
     \endcode
  
  // evaluates to true; i.e. if either one of a complex conjugate pair of eigenvalues is selected,
  // then both complex eigenvalues are selected. On exit, the parameter \a sdim will contain the
  // number of eigenvalues (after sorting) for which \a selctg is \a true. Note that complex
  // conjugate pairs for which \a selctg is \a true for either eigenvalue count as 2.
  //
  // The \a info argument provides feedback on the success of the function call:
  //
  //   - = 0: The computation finished successfully.
  //   - < 0: If info = -i, the i-th argument had an illegal value.
  //   - > 1,...,\a n: The QZ iteration failed. (A,B) are not in Schur form, but \a alphar(j),
  //          \a alphai(j), and \a beta(j) should be correct for j=\a info,...,\a n-1.
  //   - > \a n: see online reference for details.
  //
  // For more information on the sgges() function, see the LAPACK online documentation browser:
  //
  //        http://www.netlib.org/lapack/explore-html/
  //
  // \note This function can only be used if a fitting LAPACK library, which supports this function,
  // is available and linked to the executable. Otherwise a call to this function will result in a
  // linker error.
  */
  inline void gges( char jobvsl, char jobvsr, char sort,
                    int (*selctg)( const complex<float>*, const complex<float>* ), int n,
                    complex<float>* A, int lda, complex<float>* B, int ldb, int* sdim,
                    complex<float>* alpha, complex<float>* beta, complex<float>* VSL, int ldvsl,
                    complex<float>* VSR, int ldvsr, complex<float>* work, int lwork, float* rwork,
                    int* bwork, int* info )
  {
     BLAZE_STATIC_ASSERT( sizeof( complex<float> ) == 2UL*sizeof( float ) );
  
  #if defined(INTEL_MKL_VERSION)
     BLAZE_STATIC_ASSERT( sizeof( MKL_INT ) == sizeof( int ) );
     using ET = MKL_Complex8;
     using Selctg = MKL_INT (*)( const ET*, const ET* );
  #else
     using ET = float;
     using Selctg = int (*)( const ET*, const ET* );
  #endif
  
     cgges_( &jobvsl, &jobvsr, &sort, reinterpret_cast<Selctg>( selctg ), &n,
             reinterpret_cast<ET*>( A ), &lda, reinterpret_cast<ET*>( B ), &ldb, sdim,
             reinterpret_cast<ET*>( alpha ), reinterpret_cast<ET*>( beta ),
             reinterpret_cast<ET*>( VSL ), &ldvsl, reinterpret_cast<ET*>( VSR ), &ldvsr,
             reinterpret_cast<ET*>( work ), &lwork, rwork, bwork, info
  #if !defined(INTEL_MKL_VERSION)
           , blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1)
  #endif
           );
  }
  //*************************************************************************************************
  
  
  //*************************************************************************************************
  /*!\brief LAPACK kernel for computing the generalized Schur decomposition for a pair of
  //        non-symmetric double precision complex column-major matrices.
  // \ingroup lapack_eigenvalue
  //
  // \param jobvsl \c 'V' to compute the left Schur vectors, \c 'N' to not compute them.
  // \param jobvsr \c 'V' to compute the right Schur vectors, \c 'N' to not compute them.
  // \param sort \c 'S' to order the eigenvalues on the diagonal, \c 'N' to not order them (see \a selctg).
  // \param selctg Logical function of two double precision complex arguments.
  // \param n The order of the matrices \a A, \a B, \a VSL, and \a VSR \f$[0..\infty)\f$.
  // \param A Pointer to the first element of the double precision complex column-major matrix \a A.
  // \param lda The total number of elements between two columns of the matrix A; size >= max( 1, \a n ).
  // \param B Pointer to the first element of the double precision complex column-major matrix \a B.
  // \param ldb The total number of elements between two columns of the matrix B; size >= max( 1, \a n ).
  // \param sdim Returns the number of eigenvalues (after sorting) for which \a selctg is \a true.
  // \param alpha Pointer to the first element of the eigenvalue numerator; size == n.
  // \param beta Pointer to the first element of the eigenvalue denominator; size == n.
  // \param VSL Pointer to the first element of the column-major matrix for the left Schur vectors.
  // \param ldvsl The total number of elements between two columns of the matrix VSL \f$[0..\infty)\f$.
  // \param VSR Pointer to the first element of the column-major matrix for the right Schur vectors.
  // \param ldvsr The total number of elements between two columns of the matrix VSR \f$[0..\infty)\f$.
  // \param work Auxiliary array; size >= max( 1, \a lwork ).
  // \param lwork The dimension of the array \a work; see online reference for details.
  // \param rwork Auxiliary array; size == 8*n.
  // \param bwork Auxiliary array; size == n.
  // \param info Return code of the function call.
  //
  // This function computes for a pair of \a n-by-\a n double precision complex non-symmetric
  // matrices (\a A,\a B) the generalized eigenvalues, the generalized real Schur form (\a S, \a T),
  // and optionally the left and/or right matrices of Schur vectors (\a VSL and \a VSR). This gives
  // the generalized Schur factorization
  
                        \f[ (A,B) = ( (VSL)*S*(VSR)**T, (VSL)*T*(VSR)**T ). \f]
  
  // Optionally, it also orders the eigenvalues such that a selected cluster of eigenvalues appears
  // in the leading diagonal blocks of the upper quasi-triangular matrix \a S and the upper triangular
  // matrix \a T. The leading columns of \a VSL and \a VSR then form an orthonormal basis for the
  // corresponding left and right eigenspaces (deflating subspaces).
  //
  // The parameter \a jobvsl specifies the computation of the left Schur vectors:
  //
  //   - \c 'V': The left Schur vectors of \a (A,B) are computed and returned in \a VSL.
  //   - \c 'N': The left Schur vectors of \a (A,B) are not computed.
  //
  // The parameter \a jobvsr specifies the computation of the right Schur vectors:
  //
  //   - \c 'V': The right Schur vectors of \a (A,B) are computed and returned in \a VSR.
  //   - \c 'N': The right Schur vectors of \a (A,B) are not computed.
  //
  // Via the parameter \a selctg it is possible to select specific eigenvalues. \a selctg is a
  // pointer to a function of two double precision complex arguments returning an \c int value.
  // In case \a sort is set to \c 'N', \a selctg is not referenced, else if sort is set to \c 'S'
  // \a selctg is used to select eigenvalues to sort to the top left of the Schur form. An
  // eigenvalue \f$ alpha[j]/beta[j] \f$ is selected if
  
     \code
     selctg( &alpha[j], &beta[j])
     \endcode
  
  // evaluates to true; i.e. if either one of a complex conjugate pair of eigenvalues is selected,
  // then both complex eigenvalues are selected. On exit, the parameter \a sdim will contain the
  // number of eigenvalues (after sorting) for which \a selctg is \a true. Note that complex
  // conjugate pairs for which \a selctg is \a true for either eigenvalue count as 2.
  //
  // The \a info argument provides feedback on the success of the function call:
  //
  //   - = 0: The computation finished successfully.
  //   - < 0: If info = -i, the i-th argument had an illegal value.
  //   - > 1,...,\a n: The QZ iteration failed. (A,B) are not in Schur form, but \a alphar(j),
  //          \a alphai(j), and \a beta(j) should be correct for j=\a info,...,\a n-1.
  //   - > \a n: see online reference for details.
  //
  // For more information on the sgges() function, see the LAPACK online documentation browser:
  //
  //        http://www.netlib.org/lapack/explore-html/
  //
  // \note This function can only be used if a fitting LAPACK library, which supports this function,
  // is available and linked to the executable. Otherwise a call to this function will result in a
  // linker error.
  */
  inline void gges( char jobvsl, char jobvsr, char sort,
                    int (*selctg)( const complex<double>*, const complex<double>* ), int n,
                    complex<double>* A, int lda, complex<double>* B, int ldb, int* sdim,
                    complex<double>* alpha, complex<double>* beta, complex<double>* VSL, int ldvsl,
                    complex<double>* VSR, int ldvsr, complex<double>* work, int lwork, double* rwork,
                    int* bwork, int* info )
  {
     BLAZE_STATIC_ASSERT( sizeof( complex<double> ) == 2UL*sizeof( double ) );
  
  #if defined(INTEL_MKL_VERSION)
     BLAZE_STATIC_ASSERT( sizeof( MKL_INT ) == sizeof( int ) );
     using ET = MKL_Complex16;
     using Selctg = MKL_INT (*)( const ET*, const ET* );
  #else
     using ET = double;
     using Selctg = int (*)( const ET*, const ET* );
  #endif
  
     zgges_( &jobvsl, &jobvsr, &sort, reinterpret_cast<Selctg>( selctg ), &n,
             reinterpret_cast<ET*>( A ), &lda, reinterpret_cast<ET*>( B ), &ldb, sdim,
             reinterpret_cast<ET*>( alpha ), reinterpret_cast<ET*>( beta ),
             reinterpret_cast<ET*>( VSL ), &ldvsl, reinterpret_cast<ET*>( VSR ), &ldvsr,
             reinterpret_cast<ET*>( work ), &lwork, rwork, bwork, info
  #if !defined(INTEL_MKL_VERSION)
           , blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1), blaze::fortran_charlen_t(1)
  #endif
           );
  }
  //*************************************************************************************************
  
  } // namespace blaze
  
  #endif
  